Thermochromic luminescence and dielectric response of copper(I) iodide based MOFs as luminescent thermometer

•This compound shows fascinating luminescent thermochromic.•Dielectric relaxation was observed.•A copper-iodide based MOFs crystal. A copper(I) iodide based MOFs crystal with the formula [Cu4I4(Pz)2]n (Pz = [1,4-bis(4-pyridylmethyl)piperazine]) (1) was synthesized using a solvothermal method. The compound 1 crystallized in the monoclinic space group C2/c at room temperature and consisted of Cu4I4 clusters. Along the b-axis, an irregular window with a size of 7.8 × 31.6 Å was formed. The neighboring rotators (piperazine ring) had a long distance of 12.3 Å between their rotational axes (CH2-), making it easy to rotate. From the view of the crystal structure, 1 can serve as an ideal amphidynamic model, and an in-plane oscillatory fluctuation of the piperazine ring results from the dielectric relaxation. In addition, this compound also showed luminescence thermochromic properties, and a good linear relationship between the luminescence intensity ration of the three emission bands and the temperature was observed. Thus, this compound can be excellent as a luminescent thermometer. These findings provide a new strategy for constructing electrical and optical properties of amphidynamic MOFs.